Why this category is different
Most compounds in this library have no randomised human trial of any kind. GLP-1 receptor agonists have trials with tens of thousands of participants, prespecified primary endpoints, and independent adjudication of outcomes. The evidentiary gap between this category and everything else here is not marginal.
What the outcome trials established
Weight reduction was the finding that made these drugs famous, but it is not the finding that matters most clinically. The important result came from trials designed around cardiovascular events rather than weight.
In a population of people with overweight or obesity and established cardiovascular disease — a large share of whom did not have diabetes — GLP-1 agonist treatment reduced the incidence of major adverse cardiovascular events. That is a hard clinical endpoint: cardiovascular death, non-fatal myocardial infarction, non-fatal stroke.
Two aspects of that finding deserve emphasis. First, it held in people without diabetes, so it cannot be explained by glycaemic control alone. Second, the effect size was modest in absolute terms and meaningful at population scale — which is what outcome trials typically deliver.
Mechanism beyond appetite
There is more at work than reduced food intake. GLP-1 receptors are expressed in the cardiovascular system, and proposed additional mechanisms include direct anti-inflammatory effects, improvements in endothelial function, and reduced platelet aggregation. Which of these actually drives the outcome benefit is not settled — separating the drug's direct effects from the consequences of substantial weight loss is methodologically difficult.
Tolerability shapes everything
Gastrointestinal effects — nausea, vomiting, diarrhoea, constipation — dominate the side-effect profile and are concentrated during dose escalation. This is not cosmetic: tolerability determines whether people reach and stay at the doses where the benefits were demonstrated.
Slow titration is the intervention. Escalating faster than the protocol does not accelerate the benefit; it produces a higher discontinuation rate.
The body-composition finding
A substantial share of the weight lost is lean mass. This is often discussed as a caveat and should be treated as a clinical finding in its own right — particularly in older adults, where muscle mass is already declining.
The practical response is not to avoid the drug but to pair it with resistance training and adequate protein, which is what clinical protocols do. A trial-consistent intervention includes the training, not only the injection.
Duration and discontinuation
The trials ran for 68 to 72 weeks and beyond, and the effects were sustained during treatment. Weight regain after discontinuation is well documented and expected — these are chronic-intervention drugs, not courses. Any honest protocol includes a plan for what happens at the end.
What remains open
Several questions are genuinely unresolved: whether the cardiovascular benefit scales with the degree of weight loss, whether dual agonists produce larger outcome benefits than single agonists, and what the long-term effects are over a decade or more. Trials addressing these are ongoing.
This is the one category here where the honest summary is that the drug works, the mechanism is well characterised, and the open questions are about magnitude and duration rather than existence.